The invention relates to a process for the preparation of polyisoprene by polymerizing isoprene in an inert diluent in the presence of a beta-TiCl.sub.3 -containing catalyst and an activator.
The Netherlands patent application No. 7316397 discloses a process for the preparation of polyisoprene by mixing TiCl.sub.4, trihydrocarbylaluminum and ether, then aging the reaction mixture thus obtained and adding to this aged catalyst mixture, prior to it being brought into contact with isoprene, a dihydrocarbylaluminum chloride. This process gives polyisoprene with a high cis-1,4 content. Especially at high (40.degree. C.) polymerization temperatures, however, the degree of isoprene conversion is not very high. Degree of conversion is here defined as the amount of isoprene converted, expressed as a percentage of the total amount of isoprene added to the mixture subjected to polymerization.
The European patent application No. 0021478 discloses a process for polymerizing an alpha-olefin with the aid of a catalyst containing a titanium halide and a reaction product of a hydroxy-aromatic compound with in both ortho positions a secondary or tertiary alkyl group, a halogen-free organoaluminum compound and an organoaluminum halide, or of the aforesaid hydroxy-aromatic compound and an organoaluminum halide. This process is not concerned with polymerization by means of a beta-TiCl.sub.3 containing catalyst, nor with the polymerization of dienes.